Descaling reactor vessels without harming the lining that protects them

Project facts

Why does a decommissioning need descaling?

Decommissioning is not demolition — it is a controlled return of the site to its pre-operations state. A High Pressure Acid Leach facility precipitates mixed sulfide as part of its process, and years of operation leave that scale bonded to the inside of the reactor vessels. Before the plant can hand its site back, the vessels have to come clean — completely, verifiably, and without destroying the equipment in the process. Dezu knew this plant: we descaled it during its 2023 shutdown, and the decommissioning campaign brought us back for the full vessel scope.

What makes mixed sulfide scale hard to remove safely?

Three problems arrive together. The scale is hard and thick, so mechanical chipping takes forever. The work happens inside a confined vessel at elevated heights, so every added tool and hour is added risk. And the vessel walls are lined with acid-resistant brick that must survive the cleaning — the lining is the equipment's integrity, and impact tools that are aggressive enough to beat the scale are aggressive enough to break the bricks. Traditional descaling loses on all three at once: too slow, too dangerous, too damaging.

How did Dezu remove it without damaging the brick lining?

High pressure water attacks the deposit at the scale-to-brick interface without hammering the lining behind it — the same physics that lets hydro demolition strip concrete while preserving rebar, translated into a vessel. We proved the parameters on a pilot vessel first, against the real scale. The campaign then ran top-down, level by level, so falling scale, crew positioning, and energized water inside a confined space stayed controlled at every stage.

What did five months inside reactor vessels teach us?

Water quality proved to matter as much as water pressure. Cavitation — the same collapsing-bubble energy that erodes scale — works on the contractor's own equipment too, and managing its effect on seals, packing, and metal parts became part of running the job. Nozzles and waterjet PPE wore at rates far beyond normal duty, so consumables planning became a production discipline of its own. These are the operating costs of doing months of ultra high pressure work inside a vessel, and knowing them in advance is part of what a client hires.

What was the result?

The reactor vessels were descaled through the full campaign with the brick lining intact, against the contractual hand-back standard. The engagement closed on schedule after five months — the proof point that hydro demolition equipment scales from a single repair to an entire decommissioning program.